Various products including automotive vehicle are typically painted using an electrostatic spray process. An electrostatic spray process uses a conductor that applies a potential difference between paint spray particles and the device to be painted. A modification of electrostatic spraying is a bell-atomizer spray process. For large products such as automotive vehicles, these systems are typically automated.
In the bell-atomizer process, electrostatic forces are combined with shaping air to direct paint toward the component to be painted. An application head has a bell cup that rotates at speeds in excess of about 30,000 rpms. The rotation of the bell cup acts to atomize the paint which is directed through the cup. Once atomized, the paint interacts with the shaping air through drag forces that divert the paint toward the target. An electric potential is applied to increase the axial momentum of the particles to increase the paint transfer efficiency.
One problem with known bell-atomizer automated spray processes is that due to side drafts, downdrafts, shaping air turbulence and interaction with the target, some air recirculates about the support housing and bell housing. As a result, paint may drip from the support housing and bell housing onto the component being painted. If this occurs, the component typically must be repainted and thus the cost of the component is increased.
To prevent drips from accumulating on the support housing and the bell housing, the automated process is typically stopped at frequent intervals so the support housing and bell housing can be cleaned. This also increases the cost of the product, particularly in assembly plants operating at full capacity. One known device for electrostatic spraying has a planar electrostatic shield surrounding the paint application head. The planar shield is spaced apart from the application head. Therefore, it is believed that the movement of the application head will result in air currents that cause paint to bypass the shield and buildup on the paint application head. Particularly, it is believed that paint will buildup on the sides of the application head resulting in the aforementioned drips. The buildup may be increased by spray from adjacent heads.
It would therefore be desirable to provide an improved paint application process that reduces the amount of maintenance as well as reduces the amount of repair costs for paint drip from the application head to the components to be painted.